1. A total of 29 shellfish samples, comprising 14 mussel (Mytilus edulis), 5 oyster (Crassostrea gigas) and 10 scallop (Pecten maximus) samples were collected from five coastal regions and seven offshore locations around Scotland during January to March 2006.

2.The concentrations and composition of polycyclic aromatic hydrocarbons (PAHs) and the concentrations of trace metals (TM), chlorobiphenyls (CBs) and organochlorine pesticides (OCPs) were determined in all three species.

3. The total measured PAH concentration in 12 out of the 14 mussel samples analysed was less than 150 ng g-1 wet weight. One of the remaining samples had a total PAH concentration in excess of 250 ng g-1 wet weight.

5. The total measured PAH concentrations in scallop adductor muscle were, with one exception, all less than 50 ng g-1 wet weight tissue while the total measured PAH concentrations in scallop gonad tissue were all greater than 50 ng g-1 wet weight.

7.Trace metal concentrations in mussels generally did not exhibit a high variance between sites but concentrations of some of the elements exceeded natural background [reference] concentrations. All trace metal concentrations determined in mussels and scallop adductor tissues were within the EEC Guideline and Imperative concentrations. Oyster tissue concentrations of copper and zinc were found to be higher than those in mussels. The other elements were generally lower than those found in mussels. Concentrations of trace metals in scallop adductor muscle were, without exception, lower than the corresponding gonad tissue samples.

8. Chlorobiphenyl and organochlorine pesticide concentrations determined in mussels were, with one exception, within the Environmental Assessment Criteria (EAC) established by OSPAR for mussels. An EAC has not been established for either oysters or scallops, but CB concentrations were, with one exception, within the EAC established for mussels and within ranges found in previous studies.

9. In respect of consumption of shellfish and their impact on health, benzo[a]pyrene (B[a]P) is one of the PAHs in the highest category of concern regarding its possible carcinogenic effects. It is concluded that the concentrations of B[a]P in shellfish found in this survey, combined with the intake from an average diet, are within concentrations considered as being of low concern for human health. The concentrations of lead, cadmium and mercury, chlorobiphenyls and organochlorine pesticides determined in all shellfish samples from this survey do not raise health concerns in respect of consumption by the general public.